Passive infrared (PIR) sensors detect intruders moving within its field of view by detecting the heat radiated by an intruder. Typically, the ideal mounting location for the sensor is close to the ceiling in the corner of the space to be protected. As such, most PIR sensors available on the market today are designed for corner mounting (such as shown in FIG. 1). The problem with this arrangement is that it is difficult to pre-wire this type of sensor in a new construction project. In a new construction project, an alarm installer will pre-wire the system with wiring harness 6 and place single gang junction boxes in the locations where the sensors will be located. After the construction is complete (drywall 8 installed and painted) the installer will return and install the sensors in the junction boxes. However, this is not possible for corner mounted PIR sensors 2 since the corner of the room is constructed with several 2×4 studs 4 and will not readily accept a junction box without compromising the structural integrity. Existing flush mount detectors try to solve this problem but they are designed for wall mount only and because of this the field of view will not completely protect a rectangular room.